A. PC12, a cell derived from an adrenal medullary tumor, contains adenosine receptors that exhibit high affinity for the adenosine receptor agonists, 5'-N-ethylcarboxamideadenosine and N6-phenylisopropyladenosine. The receptor is of the Ra subclass and mediates stimulation of adenylate cyclase in isolated PC12 plasma membranes. The adenosine receptor agonists produce modest effects on PC12 cells but act synergistically with nerve growth factor to promote induction of ornithine decarboxylase and neurite outgrowth. B. Like insulin, N6-phenylisopropyladenosine (PIA), is a potent inhibitor of lipolysis in fat cells. When normally occurring adenosine is removed from the medium, PIA, again like insulin, stimulates glucose transport into fat cells. The adenosine analog is effective at nanomolar concentrations and stimulates transport to a level approaching that seen with insulin.